Database Application Project ?

Hello, if you can help with a query about coursework here the condition

Requirements:
The base is WordPress. The aim is to survey. Each user registers and selects names of courses they want to attend.
Explore the structure!

A. For each course, how many people have written?
2. For each course, to display a list of subscribers with it?
3. To calculate the average how many courses you have asked of those who have completed the course?
The total number scored divided by the total number of courses